摘要:

This paper describes experimental measurements of flow velocity, electron temperature, and density performed in a steady, rarefied, free jet of argon plasma. The plasma jet is generated by an arc discharge. The axial profiles of the flow velocity, electron temperature and density, and ion saturation currents are determined over a length of 60 cm starting from the nozzle exit. The radial profiles of these quantities are measured in the subsonic zone of the plasma flow. The electron temperature and density are deduced from the characteristic of a single, cylindrical electrostatic probe. The experimental conditions are such that the Debye length &lgr;D ≪ probe diameter &fgr; ≪ mean free path. The velocity of the flowing plasma is determined from the ion saturation currents of two mutually perpendicular probes. The method of Kanal is used without a correction factor on the ion current collected by the perpendicular probe.

ISSN:0021-8979    

DOI:10.1063/1.336027

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Semiconductor‐insulator‐semiconductorn+‐SI‐n+InP structures have been used effectively for current confinement in channeled substrate buried heterostructure lasers. The semi‐insulating (SI) layer is produced by the implantation of Fe into an+‐InP substrate. The properties of this implanted layer and the role of the deep acceptor levels of Fe in controlling the transport properties of SI‐InP are studied in this and the following paper (Part II). The principle of compensation is discussed and applied to the implanted layer, and current injection phenomena are described, emphasizing the important role of space‐charge‐limited (SCL) current. The electrical characteristics of then+‐SI‐n+structures reveal the classic trap‐controlled SCL current behavior at low temperatures with a trap‐filled limit achieved at 1.2 V, and an approximately trap‐free SCL current at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.336028

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The properties of semi‐insulating (SI) Fe‐implanted InP are studied via the electrical and optical properties ofp+‐SI‐n+InP diodes. The current‐voltage‐temperature characteristics reveal a rich variety of transport processes in which the deep levels of Fe play a prominent role, including tunneling and field‐assisted thermionic emission from these levels, and space‐charge‐limited double‐injection current effects. From the analysis of these currents, different experimental estimates of the position of the deep levels have been obtained. These are compared with a direct experimental determination of their position from the measurement of the photocurrent spectra of thep+‐SI‐n+diodes. These results establish the position of the iron acceptors at a level lying between 0.60–0.65 eV below the conduction band minimum. Capacitance spectroscopy of thep+‐SI‐n+diodes revealed additional defect levels and carrier freeze‐out effects at low temperatures.

ISSN:0021-8979    

DOI:10.1063/1.336029

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

We present results establishing a relationship between epitaxial layer defect density and starting substrate perfection for siliconp/p+epitaxy. Using these results we demonstrate that control of the layer defect density at a level <20/cm2is reproducibly accomplished. At this level, the defects are primarilySpits. The density of stacking faults and dislocations is kept at <1/cm2.

ISSN:0021-8979    

DOI:10.1063/1.336030

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This paper reports on depth profiles of Mn implants, after annealing, obtained by secondary ion mass spectrometry. Two types of samples implanted with manganese were studied: unintentionally dopedn‐type (5–10×1015ecm−3), andn‐type S‐doped (n=5×1018ecm−3) substrates. In unintentionally doped substrates it is found that Mn exhibits a well‐defined two‐species diffusion front as other acceptors: Be, Zn, or Cd. On the contrary in S‐doped substrates it does not move. The study of the correlations between the movement of the residual impurities and the implanted Mn atoms, or Zn in a comparative sample, has led us to propose a model based on an interstitial‐substitutional reaction involving the impurity sites and taking place in the bulk of the semiconductor.

ISSN:0021-8979    

DOI:10.1063/1.336031

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A self‐consistent solution for the effective elastic properties of polycrystalline and perfectly disordered multiphase composites has been discussed by using theT‐matrix method under certain suitable approximations. Compared to the existing formulas these new relations for the disordered composites are very useful in practical situations for a quick and more accurate estimate of the effective elastic properties, in particular for a case where the composite has components with widely different values of the elastic constants. For comparison we have discussed the results based on Kro¨ner’s theory which also purports to solve the same problem. It is found that the two solutions do not agree. To resolve the difference we take help of Hill’s exact solution of the composite problem when the components have equal rigidities. It is found that while Kro¨ner’s theory is inconsistent with the exact result the present self‐consistent solution analytically reproduces it. Another interesting finding of the present investigation is that the approximations made in obtaining the self‐consistent solution are exact in the limit of composites with equal‐shear moduli. Finally it is indicated that although the results for composites have been derived for isotropic and cubic components it can be easily adapted for a composite with noncubic components.

ISSN:0021-8979    

DOI:10.1063/1.336032

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The response of piezoresistance gauges to dynamic stress loading is analyzed in a general framework which is based on the elasto‐plastic properties of the gauge material. This analysis is then applied to manganin transducers on which a relatively large number of empirical calibration curves has been determined in the past 20 years. It is shown that most of the apparent discrepancies between these calibrations can be accounted for by considering the different stress and strain states for wire gauges and foil gauges. We also show how the low stress calibration for manganin wire can be accounted for by considering the nonhydrostatic nature of the material in which the gauge is embedded.

ISSN:0021-8979    

DOI:10.1063/1.336033

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Chromite formation was observed in experiments with a flash‐heating hemispherical‐implosion system, when a cylindrical steel sample holder, with stainless‐steel plug, containing a graphite/iron mixture was compressed by the implosion. The formation of chromite was observed and verified by x‐ray diffraction, scanning electron microscopy, and chemical microanalysis. The diffusion rates of Cr from the plug to the sample were as high as 102–103cm2s and growth rates of chromite crystals were as high as 0.3–0.4 ms−1. The foregoing could be inferred from the observations of the recovered specimens. Possible ways of chromite formation and the causes for the unusually high diffusion and crystal‐growth rates are discussed.

ISSN:0021-8979    

DOI:10.1063/1.336034

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Imperfection (cracking, stress) in (0001)GaN/(0001)&agr;‐Al2O3grown by using the metalorganic chemical vapor deposition (MOCVD) or chemical vapor deposition (CVD) method is investigated. First, the epitaxial relation is confirmed by using the oscillating‐crystal method. Subsequently, imperfections, especially cracks, are observed in detail by optical microscopy and x‐ray diffraction topography. Cracking occurs at the layer thickness larger than 13 &mgr;m in the crystals having epitaxial layers of good quality, while it does not appear even at the thickness of 30 &mgr;m in crystals including inferior layers. Finally, stress in the layer and in the substrate are determined by measuring the warp of the wafer. Compressive stress in the good epitaxial layer is 1.6×109dyne cm−2, and in this case, cracking occurs at the maximum tensile stress in the substrate less than 3×108dyne cm−2. However, cracking does not occur even at the compressive stress of 3×109dyne cm−2in the inferior layer and at the tensile stress of 1×109dyne cm−2in the substrate. From these facts, a possible mechanism of cracking is proposed. During the epitaxial growth, microcracks occur in the substrate at the interface owing to the lattice mismatching. During the cooling, macrocracks which can be observed are grown from the already existing microcracks owing to the thermal stress. In the latter course, the cracking in the substrate must be simultaneously propagated to the epitaxial layer.

ISSN:0021-8979    

DOI:10.1063/1.336035

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Thin‐film reactions of Al/V with and without 4 at. % Cu in the Al have been studied by Rutherford backscattering, x‐ray diffraction, scanning electron microscopy, and Auger electron spectroscopy after vacuum annealing in the temperature range 300–500 °C. In the Al/V system, the intermetallic phase VAl3grows as (time)1/2with an activation energy of 2.1±0.2 eV. The presence of Cu in the Al retards the VAl3growth and alters the phase sequence.

ISSN:0021-8979    

DOI:10.1063/1.336036

出版商:AIP    

年代:1985

数据来源: AIP